Sure, many actors before him have changed their bodies in huge ways for a role, but this time seems different. Jake is insanely ripped and he's acting his heart out! There's proof in the official trailer for his new movie Southpaw (above)!

The film was written by Sons Of Anarchy creator Kurt Sutter and is going to be directed by Antoine Fuqua, who also directed Training Day!

According to a source close to the Kardashian family, the 35-year-old is taking lessons from the best — a classical pianist by the name of Oksana Kolesnikova — who was highly recommended by Kenny "Babyface" Edmonds!